Enterobius: Introduction, Classification Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes

Introduction of Enterobius

Enterobius is a genus of parasitic worms, commonly known as pinworms, which infect the human gastrointestinal tract. The most common species of Enterobius that infects humans is Enterobius vermicularis, also known as the human pinworm. These worms are usually found in the cecum and ascending colon of the large intestine and are typically transmitted through the ingestion of pinworm eggs, which can be found in contaminated food, water, or on contaminated surfaces such as bedding or clothing.

Pinworm infection is one of the most common parasitic infections in humans, affecting millions of people worldwide, particularly children. Although pinworm infections are generally not considered serious, they can cause a number of uncomfortable symptoms, including anal itching, irritability, and disrupted sleep. Treatment typically involves the use of medications that target the pinworms and their eggs. Preventative measures, such as practicing good hygiene and sanitation, can also help to reduce the risk of pinworm infection.

Classification of Enterobius

Enterobius belongs to the kingdom Animalia, phylum Nematoda, class Secernentea, order Oxyurida, and family Oxyuridae. The most common species of Enterobius that infects humans is Enterobius vermicularis, which is also sometimes referred to as Oxyuris vermicularis. Enterobius gregorii is another species of Enterobius that has been found to infect humans, although it is less common.

Overall, the taxonomy of Enterobius is as follows:

• Kingdom: Animalia
• Phylum: Nematoda
• Class: Secernentea
• Order: Oxyurida
• Family: Oxyuridae
• Genus: Enterobius
• Species: Enterobius vermicularis

Morphology

Enterobius vermicularis has a distinctive morphology that allows it to be easily identified. Adult pinworms are small, measuring between 2-13 mm in length and about 0.5 mm in diameter. They have a cylindrical shape and a pointed tail, which is why they are sometimes referred to as “threadworms”.

Their bodies are transparent and have fine striation, with the female being slightly larger than the male. The males have a curved tail and a blunt end, while the females have a straighter tail and a more pointed end. The females can also be distinguished by the presence of a long, thin, and cylindrical tail which protrudes from their posterior end.

Pinworms have a well-developed buccal capsule which allows them to feed on the intestinal mucosa. They do not have any special sensory organs, but they do have a ventral nerve cord and a pair of nerve rings around the pharynx.

Pinworm eggs are also distinctive in appearance, with a characteristic shape and size of about 50-60 μm x 20-30 μm. They are oval-shaped and have a flat surface on one side, and a more convex surface on the other. The eggs are also colorless and transparent, making them difficult to see with the naked eye.

Pathogenicity of Enterobius

Enterobius vermicularis, the human pinworm, is considered to be a relatively benign parasite, and infections are generally asymptomatic or only cause mild symptoms. However, heavy infestations may lead to more severe symptoms and complications, especially in children.

The most common symptom of pinworm infection is perianal itching, which can be severe and disruptive, especially at night. Scratching the anal area may lead to bacterial superinfection, skin irritation, and inflammation. In addition to anal itching, other symptoms of pinworm infection may include abdominal pain, nausea, diarrhea, and weight loss.

In rare cases, pinworms may migrate to other parts of the body, such as the vagina, urethra, or appendix, causing inflammation and pain. Chronic infection with E. vermicularis has also been linked to appendicitis, although the causal relationship is not well understood.

Overall, while E. vermicularis infections are generally not considered to be life-threatening, they can cause significant discomfort and disruption to daily life, especially in cases of heavy infestations or chronic infections. Treatment with antiparasitic medications is generally effective in eliminating the parasite and relieving symptoms.

Lab Diagnosis of Enterobius

The diagnosis of Enterobius infection is typically based on the identification of characteristic eggs or adult worms in stool or anal swab specimens.

Stool examination: The most commonly used method for detecting Enterobius infection is the “scotch tape test”, which involves applying a piece of the transparent adhesive tape to the perianal area early in the morning before bathing or using the toilet. The tape is then placed on a glass slide and examined under a microscope for the presence of pinworm eggs. Stool examination can also be used to detect adult worms or eggs in fecal samples.

Anal swab examination: This method involves inserting a cotton swab into the rectum to collect samples of mucus and fecal material. The swab is then examined under a microscope for the presence of pinworm eggs or adult worms.

Serological tests: There are no commercially available serological tests for Enterobius infection, as the presence of antibodies to the parasite does not necessarily indicate active infection.

PCR: Polymerase chain reaction (PCR) can be used to detect Enterobius DNA in the stool or anal swab specimens. However, this method is not commonly used for routine diagnosis due to its higher cost and complexity.

Treatment and Prevention of Enterobius

Treatment of Enterobius infection usually involves a single dose of an anthelmintic medication, such as mebendazole, albendazole, or pyrantel pamoate. These medications work by paralyzing the worms, causing them to detach from the intestinal wall and be eliminated from the body in the stool. Treatment is typically repeated after two weeks to ensure complete eradication of the parasite.

In addition to medication, hygiene measures can also be effective in preventing and controlling Enterobius infection. These measures include:

1. Frequent hand washing, especially after using the toilet and before eating or preparing food.
2. Keeping fingernails short and clean to minimize the accumulation of eggs and fecal material.
3. Laundering bedding, clothing, and towels frequently in hot water to kill any eggs or worms that may be present.
4. Avoiding sharing personal items, such as towels or bedding, with others.
5. Disinfecting surfaces in the home, especially in areas where infected individuals may have come into contact, such as bathrooms.

Preventive measures include education of individuals regarding good personal hygiene practices and identification of infected individuals for prompt treatment. In cases of outbreaks in institutions such as schools or daycare centers, a public health response may be required to implement infection control measures, including screening and treatment of individuals and disinfection of surfaces.

Keynotes on Enterobius

Here are some keynotes-

• E. vermicularis, commonly known as the human pinworm, is a common parasitic infection worldwide, especially in children.
• The most common symptom of pinworm infection is perianal itching, which can be severe and disruptive, especially at night.
• Diagnosis is typically based on the identification of characteristic eggs or adult worms in stool or anal swab specimens using the “scotch tape test” or anal swab examination.
• Treatment involves a single dose of an anthelmintic medication, such as mebendazole, albendazole, or pyrantel pamoate, with repeat treatment after two weeks.
• Hygiene measures, such as frequent hand washing and laundering of bedding and clothing in hot water, can help prevent and control the spread of infection.
• While Enterobius infections are generally not considered to be life-threatening, they can cause significant discomfort and disruption to daily life, especially in cases of heavy infestations or chronic infections.
• The scotch tape test is the most commonly used and reliable method for the diagnosis of Enterobius infection. It is a simple, non-invasive test that can be performed in an outpatient setting, making it a convenient and cost-effective diagnostic tool.

Further Readings

1. Isenberg clinical microbiology procedures Handbook
   2nd edition. Vol. 2
2. Merkel and Voge’s medical parasitology
   9th edition.
3. Parasitology: 12th edition
   By K. D. Chatterjee
4. District laboratory practice in Tropical countries –Part-I.
   By Monica Chesbrough.
5. Atlas of Medical Helminthology and protozoology -4th edn  -P.L.  Chiodini, A.H. Moody, D.W. Manser
6. Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji